利用和（差）角公式求下列各三角函数的值 （1） sin（-7π/12） （2）cos（-61π/12） （3）tan（35π/12

sin(-7π/12)= -sin(7π/12)= -sin﹙π/3+π/4﹚= -(sinπ/3cosπ/4+cosπ/3sinπ/4)= -(√3/2 * √2/2 + 1/2 * √2/2)= -(√6+√2)/4cos(-61π/12）= cos(61π/12)= cos(5π+π/12)= cos(π+π/12)= -cos(π/12)= -...